I. Field of the Invention
The invention relates to a turning mechanism operating alternately in opposite directions to facilitate the driving in or extraction of piles and the like.
II. Description of the Prior Art
An example of a prior art turning mechanism is disclosed in German Patent 1,709,316. In the turning mechanism disclosed therein the transfer of impact energy takes place by the interchangeably arranged bolt, which is detachably fixed in a corresponding groove-like recess of one stop member and enters the corresponding recess of the other stop member, while transferring the impact energy, without the two facing faces of the pair of stop members coming into direct contact. The bolts on such mechanisms are subject to high wear and as the bolts are easily replaceable, wear to the pair of stops can be avoided so that, even during a very long period of operation, a uniform transference of the impact energy from the rocker arm to the pile is ensured.
A disadvantage of such known turning mechanisms is that they lead to a large amount of working noise, which mainly varies as a function of the soil characteristics. The main source of noise is obviously caused by the stop members which engage with one another during each partial rotation and which serve to transfer the impact energy of the rocker arm to the pile. However, the interchangeable balance weights received in the rocker arm ends also form a considerable noise source, said noise being heard during each impact between the balance weights on the one hand and the rocker arm mounting supports receiving the same on the other hand. During pneumatic operation of the working cylinders, a further noise source results from the release of the compressed air from the cylinders with each impact. A further noise source occurs from using an additional tubular ram member arranged in the upper end of the pile which imparts additional axial balance momentum to the pile in the case of particularly difficult soil conditions. The working noise level resulting from these noise sources is well above the noise level permitted in dwelling areas as a result of existing noise regulations, so that it is necessary, when using the turning mechanism in such inhabited areas, to use costly and difficultly operable sound insulation means, such as e.g. sound absorption boxes, drill tube caps, sound insulating collars or the like, so that the working noise of the turning mechanism remains within the prescribed limits.
The additional sound insulation means necessary when using the turning mechanism in inhabited areas constitutes a considerable disadvantage as a result of the costs thereof, particularly in view of the fact that under different operating conditions, i.e. different soil conditions, different temperature conditions and other differing environmental conditions, it is necessary to use differently constructed sound insulation means, which may have to be changed.